This invention relates to Fourier transform spectrometers and specifically to a new optical interferometer mechanism for use therein.
The Fourier transform spectrometer has become a useful tool for scientific remote sensing of earth and planetary atmospheres. Use of the Fourier transform spectrometer for these purposes is described in "Fourier Spectroscopy in Planetary Research," an article written by R. A. Hanell and V. G. Kunde in Space Science Review, Vol. 18, pp. 201-256, 1975. However, Fourier transform spectrometers are very complex precision electro-optical-mechanical instruments. They require a mechanical slide mechanism that will move with optical interferometer stability. This requirement for stability has resulted in systems that are very large and heavy. Even so, they are still sensitive to tilt misalignments. The problems encountered in designing a stepping interferometer for Fourier spectrometers are set out in Spectrometric Techniques, Vol. II, Chapter 2, "First-Order Optical Design for Fourier Spectrometers," J. B. Breckinridge and R. A. Schindler, edited by G. A. Vanesse, Academic Press, 1981.
As a result of its complexity and sensitivity, Fourier spectrometers have been used sparingly in spaceflight applications where precision spectro-radiometric measurements are required. Attempts have been made to reduce the instrument's sensitivity to acceleration and the sampling errors introduced as a result of the nonuniformity of the mechanical scanning system. See U.S. Pat. No. 4,132,940, issued to Rudolf A. Schindler on Jan. 2, 1979. However, the problems inherent in a mechanical stepping scheme have not been solved.
Accordingly, the present invention contemplates an entirely new configuration for an interferometer which avoids most of the difficulties inherent in prior art mechanical scanning interferometers. The present invention results in an entirely new generation of efficient, lightweight, stable infrared remote radiometer measurement systems.